The invention relates to an internal combustion engine having two exhaust gas turbochargers which are connected in series with the turbines arranged in the exhaust tract and the compressors arranged in the intake tract.
An internal combustion engine of this type is known from DE 101 44 663 Al. The internal combustion engine is fitted with two exhaust gas turbochargers which are connected in series and of which the charger close to the engine is a high-pressure stage and the charger remote from the engine is a low-pressure stage. The compressors of the two exhaust gas turbochargers are connected in series in the intake tract, and the exhaust gas turbines of the two chargers are likewise arranged in series in the exhaust tract. In order to ensure that the high-pressure turbine close to the engine is not overloaded and thereby damaged in the upper speed and load range of the engine, a bypass is provided which bypasses the high-pressure turbine and which opens out into the exhaust gas line between the high-pressure and low-pressure turbines. Situated in the bypass is an adjustable blow-off valve which is adjusted as a function of state and operating variables of the internal combustion engine, in particular of the exhaust gas back pressure upstream of the high-pressure turbine close to the engine. A further bypass is provided for bypassing the turbine remote from the engine; an adjustable blow-off valve is also arranged in cold the bypass.
By means of the blow-off valves in the two bypass lines, it is possible for a blow-off past one or past both exhaust gas turbines to be carried out depending on the situation.
Based on the prior art, it is the object of the present invention to utilize the energy potential contained in the exhaust gas so as to increase the overall efficiency in the best possible way, that is, when the exhaust gas turbine close to the engine is active and also when the exhaust gas turbine is bypassed.